The production of anionic and cationic ionomers is known. It is also known from the literature that an insoluble mass precipitates from a mixture of a solution of cationic ionomers with a solution of anionic ionomers ("RECENT ADVANCES IN ION-CONTAINING POLYMERS" by M. F. Hoover and G. B. Butler, J. Polymer Sci., Symposion No. 45, page 16). However, ionomers such as these have not hitherto been considered for application in paint technology. Copolymerisates are described in FR patents 1 493 043, 1 493 044, 1 493 045 and 1 493 046, which are obtained by precipitation of anionic and cationic polymers by mutual neutralisation. The thus prepared copolymerisates can be used for different purposes such as forming of films, preparation of fibers amd for preparation of coatings.
In industry, workpieces are mainly painted with coating compositions which, after application, are cured by heating to temperatures of 80.degree. to 200.degree. C. in baking ovens. In chemical terms, the cured process generally involves crosslinking of the binder system.
Self-crosslinking and externally crosslinkable binder systems which cure by chemical reactions are known. The functional groups which react during crosslinking may be hydroxyl groups, methylol groups, amino groups, epoxy groups, masked isocyanate groups and acetal groups. Physiologically harmful cleavage products are often formed during such chemical curing processes. In addition, heavy metal compounds sometimes have to be used as catalyst. The chemical crosslinking of lacquer binders by stoving on the surface of a workpiece is basically difficult and complicated because very little liberty is available under the given conditions for controlling and modifying the organic reaction.
The problem addressed by the present invention is to provide binder systems or coating compositions which can be cured by baking and of which the crosslinking is easy to control without the formation of cleavage products and without any need for cured catalysts, particularly heavy metal catalysts.